CASE STUDY

Date: Oct 2018
Client: Compass Builders Ltd
Project: St Mary’s Bay, Kent

Soil stabilisation for housing

Soil stabilisation and ground remediation specialist Deep Soil Mixing Ltd has used their soil mixing solutions for foundations on a high quality housing project in St Mary’s Bay, Kent.

The company’s soil stabilisation techniques are being used across the whole site under residential dwellings to prevent extreme settlements from variable ground. Soil mixing is saving valuable time on this project, estimated to be up to 18 months off the programme against a conventional solution and providing improved ground stability behind coastal defences for client Compass Builders Ltd.

The site is in an enviable position, close to a beautiful sandy beach with stunning views out across the English Channel and planning permission has been granted by Shepway District Council for the development which will be called ‘The Sands’ on a brownfield site of a former hotel and military base which has been demolished. The scheme will consist of a range of 3, 4 & 5-bedroom houses and 1 & 2-bedroom apartments and will also include a new landscaped coastal park area, car park and children’s play area.

Deep Soil Mixing Ltd has undertaken both column and mass mixing using their double rotary mixing head designed by Deep Soil Mixing Ltd Director Robert McGall, installing soil mixed columns to a depth of up to 10 metres as well as a soil mixed mattress across the whole of the site covering an area of just under 11,000m2.

The company has also used the cutter soil mixer on this project to install 200 soil mixed panels.  The Cutter Soil Mixer was specifically used on the St Mary’s Bay project to overcome some isolated areas of very stiff layers of clay which had softer soils below so it was necessary to mix through the clay into the soils below to enable remediation to take place.

In response to a foundation enquiry from the consulting engineers Considine Ltd, Deep Soil Mixing Ltd put forward various options that soil mixing could provide to deliver a design solution that saved the client time and reduced cost comparable to alternative ground engineering solutions.

Roland Cooper Chartered Civil Engineer and Director of Considine Ltd commented: “These works are shaving more than 18 months off of the programme for a conventional ‘load and settle’ solution as well as providing improved stability behind coastal defences. We do like an innovative solution here at Considine!”

Deep Soil Mixing Ltd always advise getting involved with clients and their designers as early as possible in their development process to create engineered solutions that offer real cost savings for projects including real benefits such as reduced vehicle movements and the efficient use of on site materials on their projects, which reduces the carbon footprint and offers environmentally friendly sustainable solutions.

Soil mixing was specified for use on this residential site to eliminate the differential settlement across the site. The alternative solution was to either pile the buildings which would have created huge conflicts in differential settlement or to remove soil from the site and take to landfill which again was not a cost effective or environmentally friendly solution. Soil mixing is also quieter than piling and has zero vibration which meant there was no impact on the surrounding residents.

So why consider soil mixing over other more traditional ground remediation methods:

    • Reduces construction programme
    • No need to excavate and cart away so reducing landfill tax charges
    • Zero vibration during construction
    • Minimal spoil removal
    • Wide range of soils can be treated compared to other solutions
    • Soil can be used as construction material
    • No need to bring costly and bulky materials on site
    • Environmental – Reduction of Carbon Footprint
    • Effective on different soils, including soft soils, flood plains, contaminated land, peat, silts and alluvium etc.
    • Increases bearing pressure, controls settlement and reduces permeability